China Aluminum Industry Network After extrusion, aluminum profiles often develop a ring of coarse grains along their outer edges, which can significantly affect the mechanical properties of the final product. The formation mechanism and influencing factors behind these coarse-grained rings are quite complex, and no consensus has been reached among researchers yet. One possible reason is that the metal isn't uniformly deformed during the extrusion process. The outer layer of the material experiences high friction from the mold walls, leading to greater deformation. Additionally, impurities at the end of the extrusion may gradually mix into the outer layer. During heat treatment, the surface layer is exposed to high temperatures for extended periods, allowing impurities to act as nuclei for grain growth, resulting in larger grains on the outer surface.
To prevent the formation of coarse-grained rings in finished aluminum products, several strategies can be applied:
1) Employing a reverse extrusion technique helps achieve more uniform deformation, reducing the likelihood of forming coarse grains.
2) Adding small amounts of manganese, iron, or titanium to the alloy can help minimize or even eliminate the formation of coarse-grained rings.
3) Increasing the extrusion temperature to operate within the single-phase region of the alloy can reduce the depth of the coarse-grained zone.
4) Ensuring an appropriate amount of extrusion residue is left behind can help avoid carrying non-metallic inclusions into the final product’s end.
5) Keeping the inner surface of the extrusion die clean and smooth promotes the formation of a complete aluminum sleeve, thereby reducing friction during the extrusion process.
6) Avoiding excessively high quenching temperatures can prevent unwanted grain growth during cooling.
7) Using porous dies during extrusion can also help control grain structure and improve overall quality.
By implementing these methods, manufacturers can effectively reduce or eliminate coarse-grained rings, ultimately improving the performance and durability of aluminum profiles. These techniques not only enhance the structural integrity of the product but also contribute to better production efficiency and cost-effectiveness in the aluminum industry.
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